Investigators say they have evidence a homemade bomb ripped the metrojet apart mid-flight, killing 224 people.
But Egyptian authorities say they haven't uncovered any security breach at Sharm al-Sheikh airport where the plane took off, and they also deny arresting two suspects in the case.
The Russian government had initially resisted the theory that the passenger plane had fallen victim to terrorism.
Now it has confirmed what some other countries had already concluded: that the downing of a metrojet passenger plane in Egypt's Sinai peninsula last month was an act of terror.
The head of Russia's Federal Security Service, Alexander Bortnikov, says a bomb shattered the plane in mid-air, killing all of the 224 mostly Russian passengers and crew aboard.
"Traces of an explosive of foreign origin have been found. According to an analysis by our specialists, a homemade bomb containing up to 1 kilogram of TNT detonated during the flight."
Russian President Vladimir Putin has vowed to track down those responsible.
"The murder of our people in Sinai is one of the bloodiest by the number of victims of such crimes. We won't wipe off tears over our hearts and souls. It will stay with us forever."
But the Egyptian Interior Minister, Magdi Abdel, says Cairo's investigation has yet to find any evidence of criminal action, and he denies arresting two staff from the Sharm al-Sheikh airport where the plane took off.
"When we discover that there had been a security lapse we will take the necessary measures. However, up until now, there is no evidence there was any lapse in travel procedures or security inspections."
Egyptian Prime Minister Sherif Ismail would only commit to "taking into account" the findings of the Russian investigation.
"We will include them in the overall investigation process which is being carried out by the committee made up of all international parties concerned with the event. All necessary measures, in accordance with international rules on investigations of aviation accidents, will be taken to complete the necessary procedures."
While Cairo is reserving judgment on the cause of the crash, not so Vladimir Putin who is now seeking retribution.
"We won't apply any time limits. We will search for them everywhere, wherever they are hiding. We will find them in any spot on the planet and punish them."
Russia has offered a AU$70 million reward for information on the attackers.
A branch of the self-proclaimed Islamic State has previously claimed responsibility for bringing the plane down.
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